Add regression test

src/test/abilities/delta_stream.test.ts

@@ -0,0 +1,50 @@
+import { Moves } from "#app/enums/moves";
+import { Species } from "#app/enums/species";
+import { WeatherType } from "#app/enums/weather-type";
+import { Abilities } from "#enums/abilities";
+import GameManager from "#test/utils/gameManager";
+import { SPLASH_ONLY } from "#test/utils/testUtils";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+
+describe("Abilities - Delta Stream", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+    game.override
+      .battleType("double")
+      .enemyAbility(Abilities.BALL_FETCH)
+      .enemyMoveset(SPLASH_ONLY)
+      .enemySpecies(Species.MAGIKARP)
+      .moveset([Moves.SPLASH])
+      .starterForms({
+        [Species.RAYQUAZA]: 1
+      });
+  });
+
+  it("no longer applies after transition from double to single battle", async () => {
+    await game.startBattle([Species.FEEBAS, Species.RAYQUAZA]);
+
+    expect(game.scene.arena.weather?.weatherType).toBe(WeatherType.STRONG_WINDS);
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.doKillOpponents();
+    game.override.battleType("single");
+    await game.toNextWave();
+
+    expect(game.scene.arena.weather?.weatherType).toBeUndefined();
+  });
+});